Abstract:

An inflator as well as a method of manufacturing an inflator, a module
including an inflator and an airbag module. In an inflator, especially
for a protective device in a vehicle, comprising plural components a
sealant is applied in the area of abutting components, especially a
sealant which adheres to both abutting components.

Claims:

1. An inflator (10), especially for a protective device in a vehicle,
comprising plural parts, wherein in the area of abutting parts a sealant
(42) is applied, the sealant (42) adhering to both abutting parts.

2. An inflator (10) according to claim 1, wherein the abutting parts form
at least part of the outer inflator surface and/or consist of different
materials.

3. An inflator (10) according to claim 2, wherein one of the abutting
parts comprises a part consisting of a plastic material that forms a
partial injection-molding around another of the abutting parts which is
made of metal.

4. An inflator (10) according to claim 2, wherein the part consisting of
plastic material is a base (32) for an igniter (28).

5. An inflator (10) according to claim 4, wherein the base (32) embeds
portions of a pre-fabricated igniter (28).

7. An inflator (10) according to claim 2, wherein one of the abutting
parts comprises a part consisting of metal which is an external housing
part of the inflator (10).

8. An inflator (10) according to claim 7, wherein another of the abutting
parts comprises a part consisting of plastic material which is
injection-molded to the edge of an orifice (26) in the external housing
part, in order to close the orifice 26.

9. An inflator (10) according to claim 1, wherein the sealant (42) is
applied to the transitional edge of the abutting parts from outside the
inflator (10).

10. An inflator (10) according to claim 1, wherein the sealant (42) is
introduced into a recess (54) provided at the transition of the abutting
parts.

11. An inflator (10) according to claim 1, wherein in the application
state the sealant (42) is liquid and/or is an adhesive, in particular an
acrylate adhesive.

12. An inflator (10) according to claim 1, wherein the sealant (42) can
be applied in liquid state and can subsequently be hardened especially by
UV light.

14. An inflator (10) according to claim 1, wherein the sealant (42)
contains a dye, in particular fluorescent dye, and or a dye deviating
from the plastic material of the part to which the sealant (42) is
attached.

15. A method for checking the density of an inflator (10) according to
claim 14, especially by making use of a camera, wherein the sealing bead
formed by the sealant (42) is irradiated with UV light.

16. An inflator (10) according to claim 1, further comprising an annular
filter (76) disposed upstream of discharge orifices (78) which has two
axial ends, the filter being outwardly bent, especially bent straightly,
at one of its axial ends (80, 82).

17. An inflator (10) according to claim 16, wherein the filter (76) has
the same thickness in the bent portion as in a central portion which is
adjacent to the bent portion.

18. An inflator (10) according to claim 16, wherein the filter wall,
viewed in the axial cross-section, extends substantially S-shaped between
the ends.

19. An inflator (10) according to claim 16, wherein the bent portion is
adjacent in a corner portion of the inflator (10) formed by a
circumferential wall (16) and a bottom.

20. An inflator (10) according to claim 16, wherein the filter (76) is
positioned axially braced in the inflator (10) and/or is made of a wire
mesh of wires having substantially equal cross-sections.

21. An inflator (10) according to claim 16, wherein the filter (76) is
laterally spaced apart from downstream discharge orifices (78) provided
in an external housing (12) of the inflator (10).

22. An inflator (10) according to claim 16, wherein the filter (76) is
tapered toward an axial end (80, 82), preferably at the end opposed to
the bent end (80).

23. An inflator (10) according to claim 16, wherein the filter (76) is
adjacent to inflator parts at its axial ends (80, 82) especially at the
end faces, and the radially innermost contacting position of the bent end
is located radially further outward at the associated inflator part than
the radially outermost contacting position of the opposed axial end (80,
82) at the associated inflator part.

24. An inflator (10) according to claim 16, wherein the filter (76) is
formed of wires having different thicknesses.

25. An inflator (10) according to claim 24, wherein the filter (76) has a
tapered axial end (82) in the area of which the filter (76) has a larger
length of thinner wires related to the volume than in the adjacent
portion, preferably in the entire residual area.

26. An inflator (10) according to claim 1, further comprising at least
one igniter (28), especially in the form of a pre-fabricated component,
and a combustion chamber (56) which is filled at least partly with
pyrotechnic material (58) adapted to be ignited via at least one overflow
orifice (66), characterized in that, in particular after activating the
igniter (28) for igniting the pyrotechnic material (58), the overflow
orifice (66) is movable relative to the latter.

27. An inflator (10) according to claim 26, wherein the overflow orifice
(66) is provided in a movable wall.

28. An inflator (10) according to claim 27, wherein an intermediate
chamber (62) especially receiving a boosting charge (64) which is
adjacent to the igniter (28) and which is separated from the combustion
chamber (56) by a cap (60), wherein the cap (60) is provided with the
overflow orifice (66) and is arranged in the inflator (10) such that it
is movable by activating the igniter (28).

29. An inflator (10) according to claim 1, further comprising at least
one igniter (28), especially in the form of a pre-fabricated component,
and an intermediate chamber (62) especially receiving a boosting charge
(64) which is adjacent to the igniter (28) and which is confined by a cap
(60), wherein the cap (60) is pushed onto a base (32) with its
igniter-side open end.

30. An inflator (10) according to claim 29, wherein the cap (60) is
pressed with the base (32) or is placed onto the latter while forming a
press-fit.

31. An inflator (10) according to claim 29, wherein the cap (60) is
attached to the base (32) such that it is movable by activating the
igniter (28).

32. An inflator (10) according to claim 28, wherein in the non-activated
state of the inflator (10) the cap (60) is adjacent at the end face to an
elastic component (70), especially elastic filler, the filler preferably
having a recess (72) into which the cap (60) projects in portions.

33. An inflator (10) according to claim 28, wherein the elastic component
(70) can be compressed by the movement of the cap (60).

34. An inflator (10) according to claim 32, wherein the elastic component
(70) is a filter, especially made of mesh, and that the elastic component
(70) is preferably adjacent to the inside of an end face of the inflator
(10).

35. An inflator (10) according to claim 29, wherein the base (32) is
formed by injection-molding around the igniter (28) and is preferably
provided for fixing the igniter (28) at the inflator (10).

37. An inflator (10) according to claim 26, wherein the cap 60 has at
least one lateral overflow orifice (66).

38. An inflator (10) according to claim 1, further comprising an external
housing (12), preferably having a central axis, and an igniter (28)
embedded in a base (32), the external housing (12) or a part connected to
the external housing (12) featuring a recess (34) into which the base
(32) extends and portions of the wall forming the recess (34) being bent
inwardly and an outwardly extending bulge (48) being formed distant from
the opening of the recess (34).

39. An inflator (10) according to claim 38, wherein the recess extends in
ring shape, preferably relative to the central axis.

40. An inflator (10) according to claim 38, wherein adjacent to the
recess the wall forming the recess (34) has the same wall thickness as in
the bent portion.

41. An inflator (10) according to claim 38, wherein, viewed in an axial
section, the recess (34) is S-shaped, wherein the opening portion of the
wall forming the recess (34) extends outwardly.

42. An inflator (10) according to claim 1, further comprising an external
housing (12), preferably having a central axis, and an igniter (28)
embedded in a base (32), wherein the external housing (12) or a part
connected to the external housing (12) exhibits a recess (34) into which
the base (32) extends, and wherein a wall forming the recess (34)
exhibits a bottom portion (50) having an orifice (26) through which the
base (32) extends, the bottom portion (50) having at its opposed outsides
in the area in which the base (32) contacts the same at least a
projection (52) and/or a recess (54).

43. An inflator (10) according to claim 42, wherein the edge of the
orifice (26) at an outside has a convex projection, the projection (52)
being preferably formed by a circumferential bead.

44. An inflator (10) according to claim 42, wherein the bottom portion
(50) has an especially annularly circumferential indentation (54) at the
outside opposed to the projection (52) in the area of the projection
(52).

45. An inflator (10) according to claim 42, wherein at each of the
outsides at least one projection (52) and/or at least one indentation
(54) is formed in the area in which the base (32) contacts the same,
wherein the at least one projection (52) and/or the at least one
indentation (54) extend preferably annularly around the orifice (26)
and/or wherein preferably the indentation (54) formed in the outside
facing the igniter (28) is disposed radially inside the indentation
formed at the opposed outside.

46. An inflator (10) according to claim 1, wherein the base (32) is
formed by injection-molding around at least portions of the wall forming
the indentation (54) and/or is formed of plastic material.

47. An inflator (10) according to claim 1, further comprising an external
housing (12) having at its outer circumference a flange (24), wherein the
flange (24) has an asymmetric shape so as to ensure a definite mounting
position at least in the twisting direction when fastening the gas
generator (10).

48. An inflator (10) according to claim 47, wherein in the flange (24) at
least one notch is provided as mounting positioning means (86).

49. An inflator (10) according to any claim 47, wherein plural,
especially two, three or four notches are provided which are disposed at
different angular distances along the periphery of the flange (24).

50. An inflator (10) according to claim 47, wherein as mounting
positioning means (86) a positioning orifice, especially an oblong hole
(88), is provided in the flange (24).

51. A module comprising an inflator (10) according to claim 47, wherein a
holding element (92) is provided having a counter piece engaging with the
mounting positioning means (86) of the flange (24).

52. A module according to claim 51, wherein the counter piece includes at
least one projection formed at the holding element (92).

53. A module according to claim 51, wherein the holding element (92) has
at least one fastening bolt (102), wherein the fastening bolt (102)
contacts the outer periphery of the flange (24).

54. A module according to claim 53, wherein the fastening bolt (102) does
not contact the flange (24) in the area of the mounting positioning means
(86).

55. A module according to claim 51, especially an airbag module (90),
wherein an airbag (96) is provided having an inlet orifice (98), wherein
the edge of the inlet orifice (98) is clamped between the flange (24) and
the holding element (92).

56. An inflator (10) according to claim 1, further comprising a
combustion chamber (56) filled at least partly with pyrotechnic material
(58) which is confined by combustion chamber walls, wherein all
combustion chamber walls are made of the same metal, especially steel,
especially of the same steel.

57. An inflator (10) according to claim 56, wherein the combustion
chamber walls are formed by plural interconnected parts, said parts
especially being load-bearing parts.

58. An inflator (10) according to claim 56, wherein the combustion
chamber (56) is an annular chamber.

59. An inflator (10) according to claim 56, wherein the axial height of
the inflator (10) is less than its diameter.

60. An inflator (10) according to claim 1, further comprising an external
housing (12) and a combustion chamber (56) disposed inside the external
housing (12) and containing pyrotechnic, gas generating material (58),
the wall thickness of the components of the external housing (12) being
2.0 mm or less.

61. An inflator (10) according to claim 60, wherein the external housing
comprises a diffuser (14) and a closing member (18), the diffuser (14)
and the closing member (18) being preferably shell-shaped.

62. An inflator (10) according to claim 61, wherein the diffuser (14) and
the closing member (18) are fixed to each other by a single connection
defining the strength, the connection being especially a circumferential
weld (22) between the diffuser (14) and the closing member (18).

63. An inflator (10) according to claim 61, wherein the wall thickness of
the diffuser (14) is not more than 1.5 mm.

64. An inflator (10) according to claim 61, wherein the wall thickness of
the closing member (18) is not more than 1.9 mm.

65. An inflator (10) according to claim 60, wherein upon activation a
maximum pressure in the combustion chamber of 300 bars is produced.

66. An inflator (10) according to claim 1, wherein the combustion chamber
(56) provided in the inflator (10) has a substantially toroidal shape.

67. An inflator (10) according to claim 1, further comprising an external
housing (12) and a combustion chamber (56) disposed inside the external
housing (12) which contains pyrotechnic gas generating material (58),
wherein the ratio of the maximum combustion chamber pressure occurring
upon activation of the inflator (10) to the wall thickness of the
external housing (12) is more than 150 bars/mm and preferably less than
220 bars/mm.

68. An inflator (10) according to claim 1, further comprising an external
housing (12) having plural discharge orifices (78) and a combustion
chamber (56) disposed inside the external housing (12) containing
pyrotechnic gas generating material (58), wherein the ratio of the entire
discharge area of the inflator (10) to the minimum and/or maximum wall
thickness of the components of the external housing (12) is more than 30
mm, preferably more than 34 mm.

69. An inflator (10) according to claim 1, further comprising an external
housing (12) having a diffuser (14) including a substantially cylindrical
circumferential wall (16) and comprising a combustion chamber (56)
disposed inside the external housing (12) and containing pyrotechnic gas
generating material (58), wherein the ratio of the diameter of the
diffuser (14) to the minimum wall thickness of the external housing (12)
is less than 50, preferably between 35 and 45.

70. An inflator (10) according to claim 1, further comprising an external
housing (12) having a diffuser (14) including a substantially cylindrical
circumferential wall (16) and comprising a combustion chamber (56)
disposed inside the external housing (12) and containing pyrotechnic gas
generating material (58), wherein the ratio of the diameter of the
diffuser (14) to the maximum axial height of the inflator (10) is approx.
1.8.+-.0.2, preferably 1.8.+-.0.1.

71. An inflator (10) according to claim 1, further comprising an external
housing (12) including a flange (24) at its outer periphery, wherein the
flange (24) is circumferential in a closed manner and is preferably
planar and/or that the flange (24) is formed to be free of screwing
orifices.

72. An inflator (10) according to claim 1, further comprising an external
housing (12) having a flange (24) at its outer periphery, wherein the
flange (24) is circumferential in a closed manner and is preferably
planar, and/or that the flange (24) exhibits an annular clamping surface
for the airbag (96) having a width ranging from 5 to 12%, preferably from
8 to 11% of the maximum diameter of the external housing (12).

73. An inflator (10) especially for a protective device in a vehicle and
preferably according to claim 1, comprising an external housing (12)
having a flange (24) at its outer periphery, wherein the flange (24) is
circumferential in a closed manner and is preferably planar, and/or in
that the flange (24) exhibits an annular clamping surface for the airbag
(96) having a width ranging from 5 to 8.5 mm, preferably from 5.5 to 7.5
mm.

74. An airbag module (90) comprising an inflator (10) according to claim
1, the airbag module (90) further comprising an external housing (12)
having a flange (24) at its outer periphery, an airbag (96) having an
inlet orifice (98) defined by an orifice edge (100), and comprising a
clamping element (104) opposed to the flange (24) for clamping the
orifice edge (100) between itself and the flange (24), wherein the
orifice edge (100) is clamped by such force and the clamping surface is
designed such that the lateral displacing force produced by a maximum
pressure in the airbag (96) at the orifice edge (100) is between 10 and
80%, preferably between 20 and 50% less than the frictional force
generated by the clamping force between the orifice edge (100) and the
flange (24) and the clamping element (104).

75. An airbag module (90) comprising an inflator (10) according to claim
1, the airbag module (90) further comprising an external housing (12)
having a flange (24) at its outer periphery, an airbag (96) having an
inlet orifice (98) defined by an orifice edge (100), and comprising a
clamping element (104) opposed to the flange (24) for clamping the
orifice edge (100) between itself and the flange (24), wherein the
clamped portion of the orifice edge (100) the inflator (10) has only one
or more recesses, especially a hole or a notch serving for
circumferential positioning but especially not for mounting the inflator
(10) to a module.

76. An inflator (10) according to claim 1, further comprising an external
housing (12) having a diffuser (14) including a substantially cylindrical
circumferential wall (16) including plural discharge orifices (78) and a
closing member (18) which is welded with the diffuser (14), wherein the
diffuser (14) and the closing member (18) are preferably in the form of a
shell and wherein the discharge orifices (78) are covered at the inside
of the diffuser (14) by a tamping (84), preferably in the form of a
tamping film, and the tamping (84) is spaced apart from the inner edge of
the closing member (18), especially a weld (22), preferably a laser weld,
between the diffuser (14) and the closing member (18).

77. An inflator (10) according to claim 76, wherein the distance is more
than 2 mm, preferably between 2.5 and 7 mm, further preferably between 3
and 5.5 mm.

78. An inflator (10) according to claim 76, wherein the closing member
(18) has a circumferential upright edge at which it is welded to the
diffuser (14) and the smallest distance of the weld (22) from the tamping
(84) shows at least the distance values given in claim 77.

79. An inflator (10) according to claim 1, further comprising an igniter
(28) which has an igniter cap (36) containing a plastic material and
which is at least partially surrounded by plastic injection molding,
wherein the material of the igniter cap (36) and the material of the
plastic injection molding are selected such that the igniter cap (36)
melts at least partially with the plastic injection molding during
injection molding.

80. An inflator (10) according to claim 79, wherein the igniter cap (36)
and the plastic injection molding consist of the same material.

82. An inflator (10) according to claim 81, wherein the share of glass
fibers is approximately 20 to 40%, preferably approximately 30%.

83. An inflator (10) according to claim 1, wherein the inflator (10) has
an external housing (12) and the igniter (28) is connected to the
external housing (12) by means of the plastic injection molding.

84. An inflator (10) according to claim 83, wherein the external housing
(12) has an orifice (26) and the plastic injection molding is molded to
the edge of the orifice (26) especially for closing the external housing
(12) to the outside.

85. An inflator according to claim 1, further comprising a first
component (112) and a second component (114) connected to the first
component (112) by an injected plastic base (116) by at least partially
surrounding both components (112, 114) by injection molding, wherein the
first component (112) has an adhesive film (142) applied before injection
molding in a contact area (140) with the plastic base (116).

86. An inflator according to claim 85, wherein the first component (112)
is made of metal, ceramic and/or plastic material.

87. An inflator according to claim 85, wherein the first component (112)
is an inflator housing or forms a partial element of an inflator housing.

88. An inflator according to claim 85, wherein the second component (114)
is a pre-fabricated igniter closed to the outside.

89. An inflator according to claim 85, wherein the first component (112)
has an orifice (120) for receiving and mounting the second component
(114) the edge (122) of which is embedded in the plastic base (116)
during injection molding.

90. An inflator according to claim 85, wherein the adhesive film (142)
covers only part of the portion of the first component (112) surrounded
by injection molding.

91. An inflator according to claim 85, wherein the adhesive film (142)
covers the entire portion of the first component (112) surrounded by
injection molding.

92. An inflator according to claim 85, wherein the adhesive film (142)
projects from the portion of the first component (112) surrounded by
injection molding.

93. An inflator according to claim 85, wherein the adhesive film (142)
comprises a plastic film (144) and an adhesive layer (146).

94. An inflator according to claim 93, wherein the plastic film (144) is
made of the same material as the plastic base (116).

95. An inflator according to claim 93, wherein the plastic film (144) is
made of a material which is suited for establishing a connection with the
material of the plastic base (116).

96. An inflator according to claim 93, wherein the adhesive of the
adhesive layer (146) can be activated by a predetermined contact pressure
or thermal influence.

97. An inflator according to claim 93, wherein the materials of the
plastic film (144) and the plastic base (116) are selected such that
during injection-molding the plastic base (116) the plastic film (144) at
least partially melts with the plastic base (116).

98. An inflator according to claim 93, wherein the adhesive film (142),
especially the adhesive layer (146), forms a bonding bridge between the
first component (112) and the plastic base (116).

99. An inflator according to claim 98, wherein the bonding bridge is
plastically and/or elastically deformable.

100. An inflator according to claim 92, wherein the plastic film (144)
includes a thermoplastic elastomer.

101. A method for manufacturing an inflator (10), especially for a
vehicle occupant restraint system, comprising the steps of: providing a
first component (112) containing metal and/or plastic material and/or
ceramic material, providing a second component (114) to be connected to
the first component (112), applying an adhesive film (142) to the first
component (112) in a connecting area, positioning the second component
(114) relative to the first component (112), and jointly surrounding at
least partially the first and second components (112, 114) by injection
molding, thereby forming a plastic base (116) connecting the components
(112, 114).

102. A method according to claim 101, wherein a plastic film (144) of the
adhesive film (142) melts with the plastic base (116) during injection
molding.

103. A method according to claim 101, wherein during or after applying
the adhesive film (142) the adhesive of the adhesive film (142) is
activated by pressing or heating.

104. A module comprising an inflator (10, 110), an airbag (96) inflatable
by the inflator (10, 110) and a fastening means for attaching the module,
especially in the interior of a vehicle, wherein the inflator (10, 110)
is formed according to claim 101.

Description:

FIELD OF THE INVENTION

[0001] The invention relates to an inflator, especially for a protective
device in a vehicle, a module equipped with an inflator as well as an
airbag module. Further, the invention relates to a method of
manufacturing an inflator, especially for controlling the tightness of an
inflator.

BACKGROUND OF THE INVENTION

[0002] Gas generators or inflators for protective devices in a vehicle
drive e.g. parts (propping up of hoods, tensioning of the belt, shifting
of cushions or the like) or inflate airbags.

[0003] Inflators must be operable for many years for singular use, that
is, they may be exposed to high requirements in terms of stability to
environmental influences such as penetration of moisture or corrosion.

[0004] Inflators consist of several interconnected parts. Between abutting
parts a reliable connection lasting for many years is required as
protection against environmental influences from outside.

SUMMARY OF THE INVENTION

[0005] In accordance with an aspect of the invention, an inflator is
provided especially in accordance with the type described above and/or
hereinafter in which in the area of abutting parts a sealant is applied
to the parts, especially a sealant adhering to both abutting parts. Said
sealant preferably is an additional agent serving for the tightness which
is not the only connecting means between the abutting parts.

[0006] The sealant preferably adopts no mechanical or adhesive holding
function between the abutting parts which are interconnected otherwise.
That is to say, even without a sealant the inflator is designed such that
the abutting parts are fixed in position.

[0007] As the sealant adheres to both abutting parts, moisture is
prevented from penetrating the interior of the inflator.

[0008] The abutting parts to which the sealant is applied form at least
part of the outer inflator surface and/or are especially made of
different materials. The preferred embodiment provides that one part is
made of plastic material and the other is made of metal. Due to the
strongly different expansion coefficients and properties of these parts,
the invention provides an optimized protection against environmental
influences.

[0009] The part consisting of plastic material especially constitutes a
partial injection-molding around the metallic component. Although such
injection-molding also ensures a tight, even moisture-tight connection
between these parts which, apart from the form closure, also permits
adhesion, the sealant provides additional safety against environmental
influences during the service life of an inflator, as it would be
possible at least theoretically that in the course of time small gaps
might occur by virtue of the different thermal expansions and the
different expansion behavior.

[0010] It is mentioned in this context that inflators and thus the
connection of the parts and the efficiency of the sealant have to
reliably operate and act within a temperature range of at least
-40° C. to at least 120° C. In order to fulfill these
properties, the sealant exhibits high flexibility even with low
temperatures. Further properties include low viscosity in the liquid
state during application for penetrating micro-gaps, good wetting of the
different surfaces and rapid hardening, where possible.

[0011] This rapid hardening can be obtained, for instance, by the fact
that the sealant has to be applied in a liquid state and can subsequently
be hardened by UV radiation.

[0012] As already mentioned before, the sealant is used especially between
a plastic component and a metallic component in an inflator. A preferred
embodiment is the additional sealing between a base of an igniter
consisting of plastic material and the adjacent housing part of the
inflator which is usually made of metal. The inflator according to the
invention shows the sealant in the transition area between the base and
the housing part.

[0013] The base can be formed by injection-molding around the metallic
part.

[0014] Preferably, also a pre-fabricated igniter is embedded in portions
of the base, which is effectuated especially during injection-molding.

[0015] Moreover, the base preferably forms a holder for the igniter plug,
i.e. the igniter plug which is plugged onto the contact pins is held in
the base itself.

[0016] The part consisting of metal can be an external housing part of the
inflator. The sealant is applied to the parts from outside after they
have already been interconnected and not during connection of the parts.

[0017] The part consisting of metal is injection-molded, for instance, to
the edge of an orifice in the external housing part, especially for
closing the latter.

[0018] The sealant is furthermore applied to the inflator preferably not
extensively but only at the transition edge of the abutting parts. For
protecting the sealant, the latter is introduced especially in a recess
provided at the transition of the abutting parts. The sealant can fill
the recess completely or almost completely. Preferably the sealant does
not protrude outwardly vis-a-vis the recess. Especially the recess is
formed by two abutting radii of the two neighboring parts which form a
rolling V-shaped groove.

[0019] A preferred embodiment of the invention provides that the sealant
is an adhesive, especially acrylate adhesive.

[0020] The preferred mechanical, chemical and physical properties of the
sealant are stated in the claims, wherein it is emphasized that one or
more of the stated properties should be given.

[0021] When applying the sealant it is important that it is applied to all
required predetermined positions. In accordance with a preferred
embodiment and in accordance with a method according to the invention it
is provided that the sealant contains a dye, especially a fluorescent dye
by means of which the extension of the sealant can be controlled. The
color in the sealant should be clearly different from the color (if
provided) of the plastic material of the part or, more generally, the
parts to which the sealant is adjacent.

[0022] The extension of the application of the sealant can be checked even
automatically via a camera, where appropriate.

[0023] When using a fluorescent dye the sealant, and more exactly speaking
the bead formed by the sealant, is irradiated with UV light, which
permits a particularly simple, fully automated control.

[0024] The invention provides, moreover or in addition to the
afore-mentioned features, an inflator, especially according to the type
described before and/or hereinafter, in which an excellent filtering
effect is obtained. For this purpose, upstream of discharge orifices of
the inflator an annular, preferably substantially cylindrical filter is
provided in the inflator which has two axial ends. The filter extends
outwardly bent, especially linearly bent at one of its axial ends. This
bending of the filter, which is produced already during manufacture of
the filter and not as late as during mounting by applying a tension
force, imparts higher elasticity to the filter in the axial direction. In
this way, the filter can adapt very well to its adjacent walls during
mounting into the inflator and allows a safe, exactly predeterminable
pre-tensioning force. Thus, it is ensured with the constantly present
tolerances that the filter also contacts the walls and no clearances
which might cause leakage flows occur between the filter and the adjacent
wall.

[0025] In the bent portion the filter has especially the same thickness as
in a central portion which is adjacent to the bent portion. This is to
improve the elasticity and moreover is to reduce the constructed space
and the weight. Moreover, when manufacturing the filter no longer the
wire length and thus the mass has to be transported or integrated in a
particular portion so that the bending can be simply brought about by a
plastic deformation.

[0026] Preferably, the filter wall extends, viewed in axial cross-section,
substantially S-shaped between the ends, wherein the bending is part of
the "S". This, too, is to serve for increasing the elasticity. The
S-shape relates to the built-in state in which the filter is positioned
in the inflator in a preferably axially braced manner.

[0027] Especially good positional fixing as well as sealing is resulting
from the fact that the bent portion is adjacent to a corner portion of
the inflator formed by a circumferential wall and a bottom. The filter
can be positioned laterally but also axially and biased, where
appropriate, via the corner portion.

[0028] The filter is laterally spaced apart especially from discharge
orifices provided in an external housing of the inflator so that a
chamber can be formed ahead of the discharge orifices which permits a
flow through the entire filter portion and not only through the portions
of the filter positioned directly ahead of the discharge orifices.

[0029] For obtaining the axial stability and for improving the sealing
effect at the edge of the filter, for instance at an axial end,
preferably at the end opposed to the bent end, the filter can be tapered.
Such tapering can be obtained by plastic deformation of the filter or by
introducing less material in this portion. In particular, however, the
tapered end should be relatively resilient so that it can optimally adapt
to the adjacent wall during mounting in the inflator.

[0030] The filter is adjacent at its axial ends, especially at the end
faces, to the inflator parts. The radially innermost contact point of the
bent end should preferably be located at the associated inflator part
radially further outwardly than the radially outermost contact point of
the opposed axial end at the associated inflator part. This means that in
axial direction when axially bracing the filter the contact faces are
laterally offset so that a slight bending is possible. In this way, too,
the axial elasticity is to be improved.

[0031] The filter preferably consists of a wire mesh having wires of
substantially equal cross-section. According to another preferred
embodiment, the filter can also be made of wires having different
thicknesses. Usually the filters are knitted wires.

[0032] When the filter has a tapered axial end, said tapered portion can
be formed especially simply by integrating a larger length of thin wires
related to the volume than in the neighboring portion so that said
tapered portion also becomes softer.

[0033] The invention further relates to an inflator, especially according
to the type described before and/or hereinafter which excels by a rapid
ignition of its pyrotechnic material. This is obtained with an inflator
having at least one igniter, especially in the form of a pre-fabricated
component (squib as it is called). Pyrotechnic material disposed in a
combustion chamber is ignited directly or indirectly via at least one
overflow orifice by activating the igniter.

[0034] The gas and the hot particles flowing either directly from the
igniter or from the igniter and a booster charge into the combustion
chamber ignite the pyrotechnic material there.

[0035] In accordance with the invention, it is provided that after
activating the igniter for igniting the pyrotechnic material such
overflow orifice is movable or is moved relative to the former. The
igniting gas, as it is called, and the hot particles consequently do not
flow at a fixed position of the so-called propellant into the same but
brush different portions of the propellant during the igniting operation
so that the igniting area is increased on the whole. This improves the
igniting rate and thus ensures a more rapid increase in pressure.

[0036] The relative movement between the overflow orifice and the
pyrotechnic material, the so-called propellant, can be caused by relative
movements of the propellant or else, preferably, by a movable wall. The
movable wall includes the overflow orifice or orifices and moves,
so-to-speak, along the propellant and is movable relative to the latter.

[0037] In accordance with an embodiment, an intermediate chamber is
provided between the igniter and the combustion chamber. This
intermediate chamber can receive, for instance, a booster charge or else
can be filled with ignitable gas. Said intermediate chamber is separated
from the combustion chamber by a cap. The cap is provided with the
overflow orifice(s) and is arranged in the inflator such that it is
movable by activating the igniter or that it is moved after activating
the igniter.

[0038] A further peculiarity of the inflator according to the invention,
which can be employed in combination just as the other peculiarities
solely or together with one or more other ideas especially according to
the type described before and/or hereinafter, ensures easy or simplified
manufacture of the inflator. The latter includes at least one igniter,
especially in the form of a pre-fabricated component and an intermediate
chamber (especially receiving a booster charge). Said intermediate
chamber is preferably arranged, as already explained, between the igniter
and the combustion chamber. This means that the intermediate chamber is
adjacent to the igniter and the ignition gas of the igniter flows into
the intermediate chamber. The intermediate chamber itself is confined by
a cap pushed onto a base with its igniter-side open end. In the case of
previous caps, they are frequently pressed and beaded in a bore of a very
massive part or are welded to a base, which requires more complicated
manufacture, as a matter of course, than pushing onto a base provided
anyway.

[0039] The cap can be pressed with or onto the base and/or can be disposed
at the base such that it is movable or is moved when activating the
igniter. The moving force required to move the cap can be applied by the
igniting gas when activating the igniter or else by the igniting gas of
the igniter and the additional gas generated in the intermediate chamber.

[0040] In the non-activated state of the inflator, the cap preferably
should be adjacent at the end face to a resilient component, especially
to a resilient packing. Resilient packings at the edge of or in the
propellant bed are preferred to pretension the bed of pyrotechnic
material (chaotic bed). In this context, the resilient packing has a
double function, as it serves as volumetric balancing member and,
simultaneously, as a stop and more exactly speaking as a movable stop for
the cap. In order to obtain an improved compactness, the packing may have
a recess into which portions of the cap project. During its movement the
cap can compress the resilient component so that only in this way the
movement path is made possible.

[0041] The resilient component can also additionally be in the form of a
filter, especially made of knitted mesh.

[0042] It is also taken into consideration that the resilient component is
preferably adjacent to the inside of a front wall of the inflator.

[0043] The base is formed, for instance, by injection-molding around the
igniter and is preferably provided to fix the igniter at the inflator.

[0044] In accordance with an embodiment, the cap forms a partition between
the intermediate chamber and a combustion chamber which is preferably
filled with pyrotechnic material. The cap can be the only partition
between said chambers.

[0046] Inflators are activated by transmitting an electric pulse through
contact pins accessible from the outside of the inflator to an igniter
disposed inside the external housing of the inflator.

[0047] The fast and tight, especially moisture-tight, connection must be
ensured over the entire service life of the inflator.

[0048] In another aspect of the invention the inflator, especially
according to the type described before and/or hereinafter, includes an
external housing, preferably having a central axis, and an igniter
embedded in a base, the external housing or a part connected to the
external housing including a recess into which the base extends. The wall
forming the recess has portions bent radially inwardly and has an
outwardly extending bulge distant from the port of the recess. In this
way a type of undercut is formed in which the material of the base
extends radially further outwardly than the wall of the external housing
or, in the case of a non-integral design, the part connected to the
external housing in the port area. Thus the base and the igniter are
additionally secured.

[0049] The bulge can be annularly circumferential, preferably relative to
the central axis. It is also possible, however, to provide individual
bulges only at individual positions along the circumference of the
recess.

[0050] The wall forming the recess preferably has, adjacent to the bulge,
the same wall thickness as in the bulged portion, i.e. the wall is bent
as a whole and the contour at the inside follows the one at the outside.

[0051] Viewed in an axial section, the recess may be S-shaped, wherein the
mouth portion of the wall forming the recess extends outwardly.
Preferably no sharp edges or transitions are provided but a uniform
rounding of the inner wall of the recess. In this way, the plastic
material forming the base can easily fill the bulges during
injection-molding.

[0052] The invention moreover provides an inflator, especially according
to the type described before and/or hereinafter, comprising an external
housing, preferably having a central axis, and a pre-fabricated igniter
embedded in a base, the external housing or a part connected to the
external housing having a recess into which the base extends, and a wall
forming the recess having a bottom portion including an orifice through
which the base extends, wherein the bottom portion has at least one
projection and/or one indentation on its opposed outsides in the area in
which the base is adjacent to the same. This design ensures, apart from a
fast connection, also an improved tightness against possible moisture
paths from outside.

[0053] For example, the edge of the orifice may have a convex projection
at an outside. In this context, "outside" means the side facing the
outside of the inflator.

[0054] The projection can be formed by a circumferential bead, for
instance. It is possible that at this position the wall thickness of the
bottom portion is increased.

[0055] The bottom portion is formed, e.g., by a part or portion of a
closing member which, in turn, is part of the external housing of the
inflator. But for this purpose also a separate part of the inflator can
be provided.

[0056] The bottom portion preferably has an especially annularly
circumferential indentation at the outside opposed to the projection in
the area of the projection. This indentation is directed into the
interior of the inflator, for instance.

[0057] Both the projection and the optional indentation are advantageously
surrounded by or filled with the plastic material of the base.

[0058] This is of particular advantage when the base is formed by
injection-molding around at least portions of the wall forming the
recess, because in this way a tight connection is provided.

[0059] In another aspect of the invention, an inflator according to the
invention, especially according to the type described before and/or
hereinafter, comprises an external housing having at its outer
circumference a flange, the flange being non-symmetrical or having a
shape deviating from the symmetry in order to ensure an unambiguous
mounting position at least in twisting direction when the inflator is
fastened.

[0060] The non-symmetry can be advantageously obtained by the fact that at
least one notch is provided in the flange as a mounting positioning
means. As a matter of course, also other mounting positioning means
permitting a so-called indexing can be provided.

[0061] In a possible configuration plural, especially three, notches are
provided which are arranged at different angular distances along the
circumference of the flange. In this way the mounting position of the
inflator is clearly defined by simple means.

[0062] As an alternative or in addition, a positioning orifice, especially
an oblong hole, can be provided in the flange as mounting positioning
means.

[0063] The invention also relates to a module including an inflator
mentioned above and/or hereinafter. The module has a holding member at
which preferably a counter-piece engaging in the mounting positioning
means of the flange is provided.

[0064] The counter-piece can at least include a projection formed at the
holding member, for instance.

[0065] It is possible that the holding member has at least one fastening
bolt, the latter being adjacent to the outer circumference of the flange.
Preferably the fastening bolt is not adjacent to the flange in the area
of the mounting positioning means but is distant hereof.

[0066] The module can be especially an airbag module but can also be a
different assembly including an inflator, for instance a tensioning
drive.

[0067] If the module is an airbag module in which an airbag having an
inlet orifice is provided, the edge of the inlet orifice is
advantageously clamped between the flange and the holding member.

[0068] The invention further relates to an inflator, especially according
to the type described before and/or hereinafter, comprising a combustion
chamber filled at least partly with pyrotechnic material which is
confined by combustion chamber walls, wherein all combustion chamber
walls consist of the same material, especially of the same steel.

[0069] A combustion chamber wall must have a particular inherent stability
so that it is not completely destroyed after activating the inflator
during ignition of the pyrotechnic material. The pyrotechnic material is
directly adjacent to said stable combustion chamber walls and thus
contacts the combustion chamber walls in some cases for many years
without any chemical variations being intended to occur. The invention
provides that all combustion chamber walls consist of the same metal,
especially steel. So far the combustion chamber walls have been
manufactured of different materials mainly by virtue of their different
loads. The invention simplifies the concept of an inflator, for the
so-called propellant compatibility with adjacent components is ensured,
if actually all combustion chamber walls consist of the same material.
Thus only a material pairing of pyrotechnic material with combustion
chamber material has to be tested. It is especially preferred that also
possible walls delimiting the combustion chamber against the igniter
and/or against the intermediate chamber are formed of the same material,
especially of steel, and especially of the same steel.

[0070] The combustion chamber walls are especially plural interconnected
parts, these parts especially being load-bearing components. Load-bearing
components are those components which are still retained after combustion
of the pyrotechnic material.

[0071] In this context and also in connection with other peculiarities of
the invention mentioned before and hereinafter, it is emphasized that the
inflator according to the invention especially is an inflator having an
annular chamber in the form of a combustion chamber. Such inflators are
also referred to as toroidal inflators.

[0072] It is another characteristic of the inflator according to the
invention that its axial height is less than its diameter. Inflators of
this type are integrated in particular in steering wheel airbag modules.

[0073] Another aspect of the invention provides that an inflator according
to the invention, especially according to the type described before
and/or hereinafter, includes an external housing and a combustion chamber
arranged inside the external housing which contains pyrotechnic
gas-generating material, wherein the wall thickness of the component
parts, especially of the metallic component parts, of the external
housing is 2 mm or less. This saves weight.

[0074] The external housing can consist of a diffuser and a closing
member, the diffuser and the closing member preferably being cup-shaped.
The diffuser and the closing member can be fitted into each other,
wherein an upwardly bent edge of the closing member is located inside the
especially pot-shaped diffuser and is adjacent to the inner wall of the
diffuser.

[0075] The closing member and the diffuser can be fastened to each other
by one single connection defining the strength, i.e. no tension rod or
the like is provided. The connection is in particular a circumferential
weld between the diffuser and the closing member. The weld can be formed,
e.g., by laser welding. In other words, the wall thickness of the
external housing thus is in total 2.0 mm or less, wherein an overlapping
area of the parts forming the external housing (especially in the area of
the joining weld) is left out of consideration.

[0077] It is preferred that upon activation the inflator develops a
maximum combustion chamber pressure of 360 bar, 340 bar, 320 bar, 300
bar, 290 bar, 280 bar, 270 bar, 260 bar or 250 bar which the walls have
to withstand. In this way, the entire configuration of the inflator and
of the module can be optimized and the manufacture can be made more
inexpensive.

[0078] The combustion chamber preferably has a substantially toroidal
shape, wherein especially in the center of the toroid the igniter is
arranged and a booster charge is possibly arranged in an intermediate
chamber.

[0079] Preferably the ratio of the maximum combustion chamber pressure
formed upon activation of the inflator to the wall thickness of the
external housing is more than 120 bar/mm, especially more than 130
bar/mm, 140 bar/mm, 150 bar/mm, 160 bar/mm, and/or 170 bar/mm. Further
preferably the ratio of the maximum combustion chamber pressure formed
upon activation of the inflator to the wall thickness of the external
housing is less than 250 bar/mm, especially less than 240 bar/mm, 230
bar/mm, 220 bar/mm, 210 bar/mm, 200 bar/mm, 190 bar/mm and/or 180 bar/mm.

[0080] The ratio of the entire discharge area of the inflator, viz. of the
entire area of all discharge orifices of the inflator, to the wall
thickness of the external housing preferably is more than 27, 28, 29, 30,
31, 32 or 33 mm. The ratio of the entire discharge area of the inflator,
viz. of the entire area of all discharge orifices of the inflator, to the
wall thickness of the external housing preferably is more than 32, 33,
34, 35, 36 or 37 mm.

[0081] The ratio of the diameter of the diffuser to the smallest wall
thickness of the external housing preferably is smaller than 50 and/or
larger than 30, preferably between 31 and 49, especially between 32 and
48, especially between 33 and 47, especially between 34 and 46,
preferably between 35 and 45. The projecting fastening flange is not
added when measuring, but only the inflator part defining the hollow
which is formed by the external housing has to be measured. The diffuser
advantageously has a substantially cylindrical circumferential wall.

[0082] The ratio of the diameter of the diffuser to the maximum axial
height of the inflator preferably is about 1.8±0.7, especially
1.8±0.5, especially 1.8±0.4, further preferably 1.8±0.3,
especially 1.8±0.2, preferably 1.8±0.1.

[0083] It is not necessary to use a tension rod, i.e. an additional
connection between the upper and the lower area of the external housing,
but it is possible as an option.

[0084] The inflator preferably has a flat cylindrical shape and thus its
width is larger than its height.

[0085] The present invention provides further peculiarities which may be
provided in addition to or separately from the characteristics and
features mentioned before and hereinafter.

[0086] In addition, the constructed space of an inflator is to be reduced.
In this respect, the invention provides various options which can be
employed individually or in combination.

[0087] The external housing of the inflator, especially according to the
type described before and/or hereinafter, includes a flange provided at
its outer circumference which is circumferentially closed. Said flange is
preferably planar and is transformed in a transition area, which
hereinafter shall not be added to the flange, with a radius into the
actual external housing. That is to say, the flange is transformed into
the external housing. Concerning the flange width the radius is not added
in the following.

[0088] According to an idea, the flange is formed without through-holes.
Through-holes reduce the clamping area between the flange and an adjacent
component, especially an airbag clamped to the flange, so that more
support area and thus clamping area is provided without the
through-holes. Since the airbag includes an inlet orifice with an orifice
edge which is especially coated, for instance with silicone, the flange
can establish sort of an adhesive or glued connection with the orifice
edge. The missing through-holes increase the displacing force required to
displace the airbag.

[0089] It is another or an additional possibility that the airbag and the
flange have a joint annular clamping area that features a width between 5
and 12%, preferably between 6 and 11%, further preferably 8 to 10% of the
maximum diameter of the external housing of the inflator. The diameter of
an inflator reveals a lot about the generated gas volume, which in turn
allows concluding therefrom the pressure exerted on the airbag and the
displacing force of the airbag. A minimized flange diameter is obtained
by reducing the flange width to the predetermined values.

[0090] Another or an additional option provides that the annular clamping
area for the airbag has a width at the flange which ranges from 6 to 9.5
mm, preferably from 5 to 8.5 mm, further preferably from 5.5 to 7.5 mm.
This small width is clearly different from previous flange widths.

[0091] For minimizing the flange an airbag module according to the
invention may be provided which includes an inflator, especially an
afore-mentioned inflator, which at its external housing and the outer
circumference thereof has a flange, an airbag with an injection orifice
defined by an orifice edge and a clamping member opposed to the flange.
Said clamping member can be a separate ring or a separate component, for
instance a diffuser cage or the like or an inflator carrier in order to
clamp the orifice edge between the same and the flange. The clamping
force is adapted in the area of the orifice edge and the clamping area
such that the lateral displacing force occurring by the maximum pressure
in the airbag at the orifice edge is between 10 and 80%, preferably
between 20 and 50% less than the friction force generated by the clamping
force between the orifice edge, the flange and the clamping member. This
relatively simple design is sufficient, as it has turned out, to minimize
the clamping flange.

[0092] The afore-mentioned airbag module or an airbag module according to
the invention deviating herefrom provides that in the clamped portion of
the orifice edge the airbag has only an opening serving for
circumferential positioning, if at all. Consequently, no clamping orifice
is provided through which a respective screw extends. Holes in the area
of the circumferential edge of the airbag weaken the airbag fabric and
reduce the support surface. An aspect of the invention provides that such
weakening is avoided and instead the larger surface of the orifice edge
is provided for clamping.

[0093] It has to be emphasized that the individual features mentioned
before and in the following description can be combined in any way. The
invention is not restricted to be realized in individual features or in
groups of features only.

[0094] In accordance with a further aspect of the invention, the inflator,
especially according to the type described before and/or hereinafter, has
an external housing including a diffuser with a substantially cylindrical
circumferential wall having plural discharge orifices and a closing
member welded with the diffuser, wherein the diffuser and the closing
member are preferably cup-shaped and wherein the discharge orifices are
covered at the inside of the diffuser by a tamping, preferably in the
form of a tamping film, and the tamping is spaced apart from the inner
edge of the closing member, especially a weld, preferably a laser weld,
between the diffuser and the closing member. This design has the
advantage that the tamping is protected in later assembly steps and
therefore is not thermally affected especially in welding processes
during which heat is developed.

[0095] Preferably the distance is more than 2 mm, especially preferred it
is more than 2.5 mm, especially more than 3 mm. The distance preferably
amounts to less than 7 mm, especially preferably it is less than 6 mm, in
particular less than 5.5 mm. Thus the distance preferably ranges from 3
to 7 mm and further preferably from 3 to 5.5 mm.

[0096] The closing member may have a circumferential upright edge to which
it is welded with the diffuser, and the smallest distance of the weld
from the tamping amounts to at least the afore-mentioned distance values.
In this way a robust and good tamping of the discharge orifices of the
inflator can be achieved.

[0097] As mentioned already it is important that the igniter is arranged
fixedly and tightly in the inflator and remains so during the entire
service life of the inflator.

[0098] According to the invention, this object is achieved by the fact
that the inflator, especially in accordance with the above and/or below
described type, includes an igniter having an igniter cap which is at
least partly surrounded by plastic injection-molding, the material of the
igniter cap and the material of the plastic molding being selected such
that during injection molding the igniter cap at least partly melts into
the plastic injection molding, i.e. partial melting of the cap is also
included.

[0099] In this way, an especially tight and fast connection is obtained
between the plastic injection molding and the igniter.

[0100] The igniter cap can be part of the igniter itself which is
preferably supplied as a pre-fabricated part or it can be a separate
component which is attached onto the igniter before the latter is
surrounded by injection molding.

[0101] Preferably, the igniter cap and the plastic injection molding
consist of the same material. This material may contain glass fibers, the
glass fiber share preferably being approx. 20-40% by weight and
especially preferred being approx. 30%.

[0102] The plastic injection molding of the igniter advantageously forms
the basis by which the igniter is connected to the external housing. This
could also be a different component, however, which is finally in turn
connected to the external housing in order to tightly connect the igniter
to the external housing.

[0103] The external housing preferably includes an orifice and the plastic
material is injection-molded around the edge of the orifice, in
particular to seal the external housing to the outside.

[0104] Furthermore, the invention relates especially to an inflator,
preferably for a vehicle occupant restraint system and preferably
according to the above and/or below described type, comprising a first
component and a second component which is connected to the first
component through an injected plastic base in that both components are at
least partly surrounded by injection molding. The invention further
relates to a method of manufacturing an inflator.

[0105] In a conventional inflator the first component, for instance, is a
cover of a generator housing which is connected to the second component,
viz. an igniter, in that the igniter is arranged in an orifice disposed
in the cover and both parts are jointly surrounded by injection molding.
In this way, a simple connection is provided between the igniter and the
generator housing which excels by low weight and low manufacturing costs.

[0106] It is intended according to the invention to provide an inflator or
a method for manufacturing an inflator in which the junction of the
components has improved tightness.

[0107] In accordance with an aspect of the invention, in an inflator of
said type it is provided that the first component has an adhesive film
applied before injection molding in a contact area with the plastic base.
A particularly tight connection between the plastic base and the first
component is achieved by the adhesive film. In contrast to a sealing
formed by shrinking a plastic material, in the inflator according to the
invention the first component may have almost any geometry, wherein
additional geometrical elements for increasing the tightness, such as
undercuts or injection moldings around parts, can be dispensed with. Also
additional components such as a metallic film serving as bar to moisture
or an annular packing are not required. Therefore, the inflator according
to the invention can be manufactured in an especially simple and
inexpensive manner.

[0109] As mentioned already in the beginning, the first component
preferably is an inflator housing or forms a partial element of an
inflator housing.

[0110] The second component especially is a pre-fabricated igniter closed
to the outside. This igniter in general has a metallic outer shell so
that it may be advantageous when also the igniter (or only the igniter
which then has to be regarded as first component) is provided prior to
injection molding with an adhesive film forming a bonding bridge.

[0111] A particularly simple joining of the components results from the
fact that the first component has an opening for receiving and mounting
the second component whose edge is embedded in the plastic base during
injection molding. In the case of an igniter as second component, the
electric connections thereof can project from the first component,
especially the inflator housing, through the opening.

[0112] In accordance with a preferred embodiment of the invention, the
surface of the adhesive film exactly corresponds to the contacting
surface between the plastic base and the first component, whereby an
improved adhesion of the plastic base to the first component is ensured
all over the surface.

[0113] Depending on the shape of the first component, it may be
sufficient, however, when the surface of the adhesive film is smaller
than the contacting surface between the plastic base and the first
component. In this way, too, a reliable sealing can be achieved already
in many cases.

[0114] Another variant of the invention provides to design the surface of
the adhesive film to be larger than the contacting surface between the
plastic base and the first component. Then the adhesive film in addition
serves as an anti-corrosive layer.

[0115] Advantageously the adhesive film is a pre-fabricated part. It can
be applied like a known tamping film.

[0116] Preferably the adhesive film includes a plastic film and an
adhesive layer. The adhesive layer is advantageously applied directly to
the plastic film. The adhesive film can be glued with its adhesive side
onto the first component so that the adhesive layer keeps the adhesive
film fixed to the metallic first component during injection molding. The
plastic material introduced during injection molding gets into contact
with the plastic film which protects the adhesive film disposed there
below against the high temperatures.

[0117] Advantageously the plastic film consists of the same material as
the plastic base or of a material which is suited to establish a
connection with the material of the plastic base.

[0118] Preferably the plastic film melts into the plastic base when the
plastic base is injection-molded. Along a joining zone a fixed connection
is formed between the adhesive film and the plastic base. As an
alternative, the fixed connection can also be brought about by a chemical
reaction of the material of the plastic base with the material of the
plastic film.

[0119] The adhesive film, especially the adhesive layer, preferably forms
a bonding bridge between the first component and the plastic base which
of advantage is plastically and/or elastically deformable. In this way,
tensions and shearing forces occurring upon a change of temperature due
to different expansion forces of the materials can be compensated.

[0120] The adhesive can be applied to the plastic film in an exactly
defined, for instance constant layer thickness.

[0121] The adhesive of the adhesive layer can be activated or hardened
e.g. by a predetermined contact pressure or a thermal influence. For this
purpose, for instance the contact pressure during gluing or the thermal
influence by the liquid plastic material used during injection molding
can be exploited.

[0122] As material for the plastic film e.g. a thermoplastic elastomer
(TPE) is taken into consideration.

[0123] In accordance with a second aspect of the invention, a method of
manufacturing an inflator, especially for a vehicle occupant restraint
system, is provided, the method comprising the following steps. First of
all, a first component containing metal and/or ceramic and/or plastic
material and a second component to be connected to the first component
are provided. Subsequently, an adhesive film is applied to the first
component in a joining area, and the second component is positioned
relative to the first component. The first and second components are
jointly surrounded at least partly by injection molding, thereby a
plastic base connecting the components being formed. As already described
with respect to the inflator according to the invention, the first
component preferably is an inflator housing or part thereof and the
second component is a pre-fabricated igniter.

[0124] Preferably the plastic film of the adhesive film melts into the
plastic base when the two components are surrounded by injection molding.

[0125] Moreover, also all advantageous further developments mentioned with
respect to the inflator apply to the method according to the invention.

[0126] Furthermore, the object underlying the invention is to improve a
module comprising an inflator, an airbag inflatable by the inflator and a
mounting means for mounting the module, especially in the interior of a
vehicle, in such way that the manufacturing costs thereof can be reduced.

[0127] This object is achieved for such module according to the invention
by the fact that the inflator is formed in accordance with at least any
one of the claims to 1 to 103.

[0128] Further features and advantages of the invention result from the
following description of plural preferred embodiments in connection with
the enclosed drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0129]FIG. 1 shows a sectional view of an inflator according to the
invention;

[0132] FIG. 4a is a schematic plan view of the flange of an inflator
according to the invention;

[0133] FIG. 4b illustrates a variant of the flange shown in FIG. 4a;

[0134] FIGS. 5 and 6 show schematic perspective views of an airbag
supporting sheet of a module according to the invention, especially an
airbag module, comprising a mounted inflator according to the invention;

[0135] FIG. 7 is a schematic cross-sectional view of an airbag module
according to the invention comprising an inflator according to the
invention;

[0136] FIG. 8 is a schematic perspective representation of a diffuser of
an inflator according to the invention;

[0137] FIG. 9 is a schematic sectional view of the diffuser shown in FIG.
8;

[0138] FIG. 10 is a sectional view of an inflator according to the
invention;

[0139] FIG. 11 is an enlarged detail of FIG. 10 showing the connection of
a first and a second component; and

[0140] FIG. 12 is an enlarged illustration of the transition from the
first to the second component.

[0141]FIG. 1 shows an inflator 10 comprising an external housing 12 being
composed of a cup-shaped diffuser 14 having a substantially cylindrical
circumferential wall 16 and a closing member 18 which also forms the
bottom of the inflator 10.

[0142] The closing member 18 includes a circumferential upright edge 20
which is adjacent to the inside of the circumferential wall 16 of the
diffuser 14 and is fixedly connected to the same by way of a weld 22. The
weld 22 preferably extends along the entire contact surface between the
closing shell 18 and the diffuser 14 and to the outside of the inflator
10, where it fills a groove existing between the closing member 18 and
the diffuser 14. For connecting the diffuser 14 and the closing member 18
a laser welding method can be used, for instance.

[0143] At the closing member side end, the circumferential wall 16 of the
diffuser 14 is bent outwardly so that a planar flange 24 being
horizontally circumferential along the inflator 10 is formed.

[0144] The closing member 18 has a central orifice 26 which serves for
receiving a pre-fabricated igniter 28. The closing member 18 has a recess
34 including an annular portion 30 toward the central orifice 26. The
recess 34 is sort of an inversion of the external housing. This area of
the inflator 10 is illustrated in detail in FIGS. 2 and 3.

[0145] The igniter 28 is enclosed by a base 32 connecting the igniter 28
also to the closing member 18 and especially to the edge of the orifice
26 and the annular portion 30.

[0146] The base 32 consists of plastic material and is injection-molded
after introducing the igniter 28 into the orifice 26. During
injection-molding the plastic material encloses both the major part of
the igniter 28 and the edge of the orifice 26 and also completely fills
the recess 34 formed by the annular portion 30 at the outside of the
inflator 10 with the exception of an outwardly directed igniter plug
receipt 38 into which the contact pins for an electric contacting of the
igniter 28 protrude. The igniter 38 is simultaneously embedded in the
base 32 during injection molding. The orifice 26 is completely closed by
the base 32 and the igniter 28 and the recess 34 is so-to-speak lined by
the base.

[0147] In this case the igniter 28 is enclosed by the base 32 so far that
merely its upper side as well as a short upper portion of an igniter cap
36 are left open.

[0148] The igniter 28 preferably is a separate pre-fabricated component.
The igniter cap 36 is either part of the pre-fabricated igniter 28 or a
separate component placed onto the igniter 28.

[0149] The igniter cap 36 in this example consists of plastic material,
namely of a plastic material similar to that of the base 32, preferably
of an identical plastic material. A standard material having a share of
glass fiber is preferably used, wherein the glass fiber share may be, for
instance, 30% by weight. The use of a similar or identical plastic
material entails the fact that during injection-molding the igniter cap
36 melts completely or partly with the base 32 and in this way a tight
and non-detachable connection is formed.

[0150] The recess 34 can also be formed at a separate part of the inflator
10 which is connected to the external housing 12, especially to the
closing member 18.

[0151] At the outside of the recess 34 a circumferential indentation is
formed between the closing member 18 and the base 32, which indentation
is filled with a sealant 42, in this case in the form of an acrylate
adhesive.

[0152] The sealant 42 is selected such that it adheres both to the metal
of the closing shell 18 and to the plastic material of the base 32. The
sealant 42 is applied from outside after injection molding of the base 32
and is located completely outside the external housing 12 of the inflator
10 and completely in the circumferential indentation.

[0153] The sealant 42 is applied in liquid or pasty form and is hardened
by UV light. It has high flexibility also at low temperatures of up to
-40° C. It features low viscosity so that it is easy to process,
has good wetting properties both for metallic and for plastic surfaces
and adheres both to metal and to plastic material.

[0162] A dye, preferably a fluorescent dye, is added to the sealant 42.
This permits simple control whether the sealing bead has been completely
applied and the recess is completely filled with the sealant 42. When
irradiated with UV light, it can be easily recognized due to the
fluorescent dye at which position the sealant 42 is provided. If a
non-fluorescent dye is used, for the same a color other than for the base
32 and the closing member 18 is chosen so that it can be recognized by
way of the color whether the sealing bead is complete and
circumferential.

[0163] This can be checked using a camera.

[0164] Prior to mounting into an airbag module, the contact pins 40 of the
inflator 10 are connected via a short-circuit bridge 44. The igniter plug
receipt 38, the base 32 and the sealant 42 are covered in this state by a
laminate film 46 and are protected against environmental influences in
this way.

[0165] The wall forming the recess 34 is arc-shaped in portions in the
radial direction r (cf. FIG. 3) in such a manner that one or more bulges
48 extending in radial direction away from the recess 34 are formed. The
inflator 10 has a central axis A (cf. FIG. 1). Relative to this central
axis A the arc forming the bulge 48 in this example extends in ring shape
around the recess 34.

[0166] It is also possible to form the bulge 48 in circumferential
direction intermittently and to provide only one or more separate bulges
48 along the circumference of the recess 34. The extension of the wall is
shown in broken lines in FIG. 3. The wall thickness of the wall of the
recess 34 is unchanged in this case vis-a-vis the wall thickness outside
the bulge 48.

[0167] In the section shown in FIG. 3 the wall of the recess 34 forms an
S-shaped curve in the area of a bulge 48, the opening portion (lower
axial end) of the wall forming the recess 34 extending outwardly.

[0168] Apart from the annular portion 30, the recess 34 includes a bottom
portion 50 which is connected to the annular portion 30 toward the
interior of the inflator 10. The bottom portion 50 also forms the edge of
the orifice 26. At the bottom portion 50 an annularly circumferential
projection 52 is formed at the edge of the orifice 26 toward the outside
of the inflator (provided with reference numerals only in FIG. 3). The
projection 52 forms a convex shape and is shaped without any sharp edges.
On the opposed side (inner side) the bottom portion has an indentation
preferably rectangular in profile which extends equally circumferentially
along the edge of the orifice 26 and whose orifice is directed toward the
interior of the inflator 10.

[0169] Both the groove 54 and the projection 52 are enclosed by liquid
plastic material when the base 32 is injection-molded so that a fast and
tight connection to the base 32 is formed which also withstands
temperature variations and constitutes an additional support during and
after solidification of the plastic material. Also the groove 54 is shown
with reference numeral in FIG. 3 only.

[0170] Inside the external housing 12 an annular, thus substantially
toroidal combustion chamber 56 is formed (cf. FIG. 1) which is filled
with a known pyrotechnic gas-generating agent 58, indicated by some
tablets in this case.

[0171] Toward the central axis A of the inflator 10, the combustion
chamber 56 is confined by a cap 60 enclosing the igniter 28 and the
portion of the base 32 located inside the inflator 10 as well as in
addition a free space in the form of an intermediate chamber 62. The
intermediate chamber 62 is filled with a boosting charge of known
pyrotechnic gas-generating material 64.

[0172] The cap 60 (cf. FIG. 2) has plural overflow orifices 66 providing a
communication between the intermediate chamber 62 and the combustion
chamber 56. In this example, the cap 60 is made of steel. It is closed at
the upper end and open at the lower end and has a substantially
cylindrical wall in which the overflow orifices 66 are disposed. The cap
60 is outwardly bent at the open end so that a short flange 68 is formed
(cf. FIG. 2). After introducing the boosting charge 64, the cap 60 is
merely pushed onto the base 32 and is possibly pressed with the same or
pushed onto the same forming a press-fit. Fastening by welding is not
provided. This leads to the fact that, when activating the inflator 10
and igniting the igniter 28, the cap 60 can move in the upward direction,
i.e. away from the igniter 28. In this way, in the course of the burning
operation also the overflow orifices 66 move upwards, i.e. relative to
the propellant. Thus further portions of the propellant bed in the
combustion chamber 56 contact the hot gases flowing out of the
intermediate chamber 62 and are ignited.

[0173] The upper portion of the combustion chamber 56 in FIG. 1, viz. at
the side of the external housing 12 opposed to the igniter 28, is
provided with an elastic component 70, in this case a filler or volume
compensating element which contacts the upper side of the diffuser 14.
The elastic component 70 is formed of a wire mesh here and can be
compressed when the cap 60 moves. Further moving space for the cap 60 is
gained from the bulge of the inflator 10 during gas formation during
which the upper side of the diffuser 14 is slightly raised.

[0174] The elastic component 70 has a central recess 72 into which the cap
protrudes up to a step and whose upper end portion is somewhat smaller
than the diameter of the cap 60 in order to counter the movement of the
cap 60 by a defined moving resistance.

[0175] In this case the cap 60 constitutes the only partition wall between
the intermediate chamber 62 and the combustion chamber 56. It is possible
that the inside of the cap 60 is lined with a protective film 74 closing
the overflow orifices 66 prior to activation of the inflator 10, wherein
the protective film 74 is destroyed upon ignition of the igniter 28.

[0176] In the state before activation shown in FIG. 1, the overflow
orifices 66 are located directly at the upper edge of the base 32 so that
they have an as large moving distance as possible in the direction of the
central axis A.

[0177] A filter 76 is arranged in the combustion chamber 56 which in this
case is ring-shaped, substantially cylindrical and extends in parallel to
the circumferential wall 16 of the diffuser 14 at a small radial distance
from the same.

[0178] The filter 76 extends over the entire height of the inflator 10 and
extends from the closing member 18 to the end face of the diffuser 14.
The filter 76 is formed of a wire mesh including wires of different
thickness.

[0179] In the circumferential wall 16 of the diffuser 14 plural, in this
example twelve, discharge orifices 78 are formed which are uniformly
spaced along the circumference of the diffuser 14 and are arranged at an
axial height. The filter 76 separates the discharge orifices 78 from the
combustion chamber 56 so that the filter 76 is located upstream of the
discharge orifices 78.

[0180] The filter 76 is pressed into the external housing 12 with axial
pre-tension.

[0181] The filter 76 includes two axial ends 80, 82 at least one end of
which is bent outwardly. In this case the bent portion forms the lower
axial end 80 and the bending extends straight. In the bent portion the
filter 76 has the same thickness as it has also in a central portion
which is adjacent to the bent portion.

[0182] In the shown example the filter 76 extends in S-shape viewed in an
axial section. At the upper axial end 82, too, a slight bending is
provided which extends toward the center of the inflator 10, however
(indicated on the left half in FIG. 1 by broken lines).

[0183] At the filter 76 the radially innermost contacting position of the
outwardly bent lower axial end 80 is located radially further outward
than the radially outermost contacting position of the inwardly bent
axial end 82 so that the end-face contact surfaces are laterally
completely offset.

[0184] The bent portion at the lower axial end 80 is adjacent to a corner
formed by the housing of the inflator 10. In this case the housing part
is formed by the closing member 18 and the lower axial end 80 of the
filter 76 is adjacent to the transition from a bottom plate of the
closing member 18 to the upwardly bent edge 20 of the same.

[0185] At the upper axial end 82 the filter 76 is tapered, as is visible
especially on the right side of FIG. 1. At this end, the filter 76 has a
larger length of thin wires, relative to the volume, than in the adjacent
area and preferably than in the residual filter, which renders the
tapered area very flexible.

[0186] This shaping permits to deform the material during axial pressing
into the inflator such that no bypass is formed for particles possibly
occurring during combustion of the pyrotechnic material 58.

[0187] The pyrotechnic material 58 in the combustion chamber 56 is
surrounded with metal on all sides, i.e. the combustion chamber wall
composed of several parts consists throughout of the same material. The
combustion chamber 56 is enclosed by the elastic filler 70, the filter
76, the cap 60 and the closing member 80. As stated before, all these
components preferably consist of the same metal, preferred of the same
steel.

[0188] The discharge orifices 78 are closed prior to activation of the
inflator 10 by a tamping 84 in the form of a tamping film. The tamping 84
is disposed circumferentially at the inside of the circumferential wall
16 of the diffuser 14 at the height of the discharge orifices 78 and
covers all discharge orifices 78. The height of tamping 84 is
approximately four times the diameter of the discharge orifices 78 in
this case.

[0189] The lower end of the tamping 84, viz. the end facing the closing
member 18, is arranged at a distance from the weld 22 which connects the
diffuser 14 to the closing member 18. The distance a from the weld 22, or
in this case equivalent to the end of the upper edge 20 of the closing
member 18, in the shown case amounts to approx. 5.5 mm and preferably
ranges from 3 to 7 mm (cf. FIG. 1). This distance is sufficient to
prevent undesired heat transfer to the tamping 84 during welding.

[0190] The external housing 12 of the inflator 10 has a relatively thin
wall thickness which in the example shown here nowhere is more than 2 mm.
In particular, the wall thickness of the diffuser is 1.5 mm and that of
the closing member is 1.9 mm. These wall thicknesses are sufficient to
withstand a combustion chamber pressure of 300 bars upon activation of
the inflator 10.

[0191] The diffuser 14 and the closing member 18 are connected only
through the weld 22 so that said weld 22 forms the only connection
between the components of the external housing 12 defining the strength.
Preferably a tension rod is not provided.

[0192] In this case, the ratio of the maximum combustion chamber pressure
to the wall thickness preferably is between 150 and 220 bars/mm.

[0193] The ratio of the entire discharge area of the inflator 10, viz. the
sum of the areas of all discharge orifices 78, to the wall thickness is
more than 30, especially more than 34 mm, in this case.

[0194] The ratio of the diameter D of the diffuser, measured by the
diameter of the circumferential wall 16, to the minimum wall thickness of
the external housing is preferably less than 50 and preferably ranges
from 35 to 45. The flange 24 is not taken into account when determining
the diameter.

[0195] The inflator 10 has substantially the shape of a flat cylinder, the
ratio of the diameter D to the maximum axial height H being approx.
1.8±0.2, preferably 1.8±0.1.

[0196] The flange 24 at the outer circumference of the diffuser 14 is
planar but unsymmetrical (cf. FIGS. 4a and b). This design offers a
positioning aid when mounting the inflator 10 into a module, for instance
an airbag module, by clearly defining the mounting position.

[0197] In the present example three notches are spaced along the
circumference of the flange 24 as mounting positioning means 86, namely
at different angular distances. The angles between the notches amount,
for instance, to 115 and 148° or to 93 and 109° in a
different example.

[0198] As an additional or alternative mounting positioning means an
orifice 88 is formed as oblong hole in the flange 84. This orifice 88 is
the only orifice provided in the flange 84.

[0199] As a matter of course, also more or fewer notches 86 or projections
instead of the notches or other suitable mounting positioning means 86
can be provided.

[0200] When mounting the inflator 10 into a module, for instance an airbag
module 90 shown in FIG. 7, the inflator 10 is fastened by a clamping or
holding element 92 (cf. also FIGS. 5 to 7). The holding element 92 has a
central opening through which the inflator 10 partly extends so that the
holding element 92 presses against the flange 24. The holding element 92
includes corresponding mounting positioning means 94 which are
complementary to the mounting positioning means 86 of the flange 24 of
the inflator 10. In this case, the mounting positioning means 94 are
formed by integrally provided projections in the holding element 92, for
instance in the form of cut-out and upwardly bent sheet sections. The
projections engage in the notches and thus clearly define the mounting
position of the inflator 10.

[0201] The orifice 88 in the flange 24 serves for defining the mounting
position of an airbag 96 (indicated in FIG. 7) which is clamped between
the flange 24 and the holding element 92 by the orifice edge 100 of its
injecting orifice 98.

[0202] The oblong hole 88 moreover can also be used for manufacturing the
inflator. In particular, in different manufacturing steps the correct
position of the diffuser (flange) with respect to other inflator
components can be ensured by a pin in the tool head which is adapted to
be engaged with the oblong hole, e.g. for orientation of the igniter
pins.

[0203] The airbag 96 likewise has an orifice at the orifice edge 100 (not
shown) which is made to match with the orifice 88 in the flange in order
to correctly position the airbag 96. The orifice 88 does not serve as
screwing orifice and constitutes the only orifice at the orifice edge 100
of the airbag 96. This means that the airbag 96 is clamped between the
flange 24 and the holding element 92 by fastening means, usually stud
bolts, which are located outside the flange 24. Thus the flange surface
is optimized.

[0204] For fastening the airbag module 90 the holding element 92 includes
fastening bolts 102, four of them in the shown example, through which the
airbag module 90 can be connected to a vehicle (not shown). The fastening
bolts 102 are adjacent to the outer circumference of the flange 24 but
offside the area of the mounting positioning means 86.

[0205] The flange 24 is circumferential and planar.

[0206] It forms an annular clamping surface for the airbag 96, wherein the
width B of the flange (the transition radius between the planar flange
portion and the circumferential wall of the diffuser 14) is between 5 and
12%, preferably between 8 and 11% of the maximum diameter D of the
external housing 12.

[0207] The width B of the clamping surface in the radial direction r
ranges from 5 to 8.5, preferably from 5.5 to 7.5 mm (cf. FIG. 9).

[0208] At the holding element 92 opposed to the clamping surface a
clamping portion 104 is defined at the flange 24 (cf. FIG. 7), which
clamping portion produces a holding force for the airbag 96 together with
the clamping surface at the flange 24. The clamping surface and the
clamping portion 104 are designed such that the forces acting via the
maximum internal pressure in the airbag 96 on the orifice edge 100 are by
20 to 50% less than the clamping force produced between the clamping
surface and the clamping element 104. The width B of the flange 24 can be
considerably reduced, so-to-speak to the minimum flange width, by this
very simple measure.

[0209] FIG. 10 shows a special embodiment of an inflator 110 according to
the invention which exhibits a first component 112, here made of metal,
in the form of an inflator housing in which an igniter device 113 is
centrally disposed. The latter comprises an igniter constituting a second
component 114 which is connected to the first component 112 via an
injection-molded plastic base 116 by the fact that both components are at
least partly jointly surrounded by injection-molding. The igniter in this
case is a pre-fabricated component enclosed by a metallic outer shell and
includes plural connecting wires 118 partly embedded in the plastic base
116 which project through an orifice 120 in the first component 112 (the
inflator housing) from the latter. The orifice 120 simultaneously serves
for receiving and fastening the second component 114 (of the igniter),
wherein especially the portion of the first component 112 forming the
edge 122 of the orifice 120 is embedded in the plastic base 116 during
injection-molding.

[0210] The upper end of the igniter in FIG. 10 is adjacent to a booster
chamber 124 filled with a boosting charge. In the shown configuration a
sleeve 126 confining the booster chamber 124 and having plural overflow
orifices 128 is placed onto the igniter or the plastic base 116. The
booster chamber 124 is surrounded by a combustion chamber 130 which is
filled with a schematically illustrated propellant 132 in the form of
tablets and at the outside is adjacent to a filter 134. At its
circumferential wall, the inflator housing has discharge orifices 136
which in the mounted state are protected against penetration of moisture
by a tamping film 138. Upon activation of the inflator 110, a gas is
generated in a known way which flows to the outside through the discharge
orifices 136 and serves, e.g., for filling an airbag of a vehicle
occupant restraint system.

[0211] In the contacting area 140 located in the vicinity of the orifice
120 or the edge 122 between the plastic base 116 and the first component
112, the latter is provided with an adhesive film 142 which was applied
already before injection-molding the plastic base 116. The adhesive film
142 only covers a portion of the injection-molded area of the first
component 112. The adhesive film 142 is fully circumferential around the
edge 122, however.

[0212] The adhesive film 142 is a pre-fabricated component and consists of
a plastic film 144 and an adhesive layer 146 directly and evenly applied
thereto (cf. FIG. 12).

[0213] The material used for the plastic film 144 in this example is the
same material as used for the plastic base 116. It is also possible,
however, to use a different material which is suited for establishing a
tight connection with the material of the plastic base 116. This can be a
thermoplastic elastomer, for instance.

[0214] The adhesive film 142 serves as a bonding bridge between the
plastic base 116 and the first component 112.

[0215] Deviating from the illustrated configuration, the surface of the
adhesive film 142 can also extend over the entire injection-molded
portion of the component 112 or project from the same, as a matter of
course. It is also possible to provide an appropriate adhesive film also
between the second component 114 and the plastic base 116.

[0216] The inflator 110 is manufactured as follows: To start with, the
first component 112 (the inflator housing) as well as the second
component 114 (the igniter) are provided and the first component 112 is
provided with the adhesive film 124 in the later connecting area of the
components (corresponding to the contacting area 140) by gluing one or
more appropriately cut pieces of the adhesive film 142 with the adhesive
layer 146 onto the corresponding positions of the first component 112, in
this case on both sides in the area of the edge 122.

[0217] The adhesive of the adhesive layer 146 can be activated or hardened
already now by the pressure during gluing. Alternatively, it is activated
or hardened by heating, which is effectuated e.g. during
injection-molding by the heat influence of the liquid plastic material.

[0218] After the adhesive film 142 was glued onto the first component 112,
the second component 114 is positioned relative to the first component
112, and both components 112, 114 are jointly surrounded by
injection-molded forming the plastic base 116, wherein both components
112, 114 are embedded at least partly in the plastic base 116.

[0219] During injection-molding the material of the plastic film 144
combines with the injected plastic material by the fact that a surface
layer of the plastic film 144 melts in a connecting zone 148 with the
plastic base 116. As an alternative, in the connecting zone 148 also a
chemical reaction can take place between the material of the plastic film
144 and that of the plastic base 116, which reaction tightly and
non-detachably interconnects the plastic film 144 and the plastic base.

[0220] The adhesive layer 146 forms a bonding bridge between the first
component 112 and the plastic base 116, the bonding bridge being
resilient and/or plastically deformable so that tensions and shear forces
occurring due to different thermal expansion coefficients of the
different materials are compensated. The adhesive layer 146 also acts as
a packing between the first component 112 and the plastic base 116.

[0221] All described features can be combined with or exchanged for one
another at the discretion of those skilled in the art.